µ‐Graphene Crosslinked CsPbI3 Quantum Dots for High Efficiency Solar Cells with Much Improved Stability

All‐inorganic perovskite CsPbI₃ quantum dots (QDs) offer much better stability for photovoltaic applications. Unfortunately, their cell efficiencies are hindered by the low carrier transport efficiency of QD‐assembled films. In addition, agglomeration‐induced phase change of QDs poses another problem for material and device degradation. Herein, the use of µ‐graphene (µGR) to crosslink QDs to form µGR/CsPbI₃ film is demonstrated. It is found that the resultant QDs film provides not only an effective channel for carrier transport, as witnessed by much improved conductivity but also significantly better stability against moisture, humidity, and high temperature stresses. The µGR/CsPbI₃ based solar cell shows increased device performance. More specifically, compared to the solar cell without the µGR treatment, V_OC is improved to 1.18 from 1.16 V, J_SC to 13.59 from 13.17 mA cm^?2, and FF to 72.6 from 68.1%, and overall power conversion efficiency to as high as 11.40 from 10.41%, a 12% increase. In addition, the instability originating from the thermal/moisture‐induced QD agglomeration is also greatly suppressed by the µGR crosslinking. The optimized device retains >98% of its initial efficiency after being stored in N₂ atmosphere for one month. Importantly, under 60% humidity and 100 °C thermal stresses, the µGR/CsPbI₃ devices show much better stability.     

Low Temperature Synthesis of Stable γ‐CsPbI3 Perovskite Layers for Solar Cells Obtained by High Throughput Experimentation

The structural phases and optoelectronic properties of coevaporated CsPbI₃ thin films with a wide range of [CsI]/[PbI₂] compositional ratios are investigated using high throughput experimentation and gradient samples. It is found that for CsI‐rich growth conditions, CsPbI₃ can be synthesized directly at low temperature into the distorted perovskite γ‐CsPbI₃ phase without detectable secondary phases. In contrast, PbI₂‐rich growth conditions are found to lead to the non‐perovskite δ‐phase. Photoluminescence spectroscopy and optical‐pump THz‐probe mapping show carrier lifetimes larger than 75 ns and charge carrier (sum) mobilities larger than 60 cm² V^?1 s^?1 for the γ‐phase, indicating their suitability for high efficiency solar cells. The dependence of the carrier mobilities and luminescence peak energy on the Cs‐content in the films indicates the presence of Schottky defect pairs, which may cause the stabilization of the γ‐phase. Building on these results, p–i–n type solar cells with a maximum efficiency exceeding 12% and high shelf stability of more than 1200 h are demonstrated, which in the future could still be significantly improved, judging on their bulk optoelectronic properties.     

Cesium Doped NiOx as an Efficient Hole Extraction Layer for Inverted Planar Perovskite Solar Cells

Organic–inorganic hybrid perovskite solar cells have resulted in tremendous interest in developing next generation photovoltaics due to high record efficiency exceeding 22%. For inverted structure perovskite solar cells, the hole extraction layers play a significant role in achieving efficient and stable perovskite solar cell by modifying charge extraction, interfacial recombination losses, and band alignment. Here, cesium doped NiO_x is selected as a hole extraction layer to study the impact of Cs dopant on the optoelectronic properties of NiO_x and the photovoltaic performance. Cs doped NiO_x films are prepared by a simple solution‐based method. Both doped and undoped NiO_x films are smooth and highly transparent, while the Cs doped NiO_x exhibits better electron conductivity and higher work function. Therefore, Cs doping results in a significant improvement in the performance of NiO_x‐based inverted planar perovskite solar cells. The best efficiency of Cs doped NiO_x devices is 19.35%, and those devices show high stability as well. The improved efficiency in devices with Cs:NiO_x is attributed to a significant improvement in the hole extraction and better band alignment compared to undoped NiO_x. This work reveals that Cs doped NiO_x is very promising hole extraction material for high and stable inverted perovskite solar cells.     

Highly Air‐Stable Single‐Crystalline β‐CsPbI3 Nanorods: A Platform for Inverted Perovskite Solar Cells

The synthesis of single‐crystalline β‐CsPbI₃ perovskite nanorods (NRs) using a colloidal process is reported, exhibiting their improved photostability under 45–55% humidity. The crystal structure of CsPbI₃ NRs films is investigated using Rietveld refined X‐ray diffraction (XRD) patterns to determine crystallographic parameters and the phase transformation from orthorhombic (γ‐CsPbI₃) to tetragonal (β‐CsPbI₃) on annealing at 150 °C. Atomic resolution transmission electron microscopy images are utilized to determine the probable atomic distribution of Cs, Pb, and I atoms in a single β‐phase CsPbI₃ NR, in agreement with the XRD structure and selected area electron diffraction pattern, indicating the growth of single crystalline β‐CsPbI₃ NR. The calculation of the electronic band structure of tetragonal β‐CsPbI₃ using density functional theory (DFT) reveals a direct transition with a lower band gap and a higher absorption coefficient in the solar spectrum, as compared to its γ‐phase. An air‐stable (45–55% humidity) inverted perovskite solar cell, employing β‐CsPbI₃ NRs without any encapsulation, yields an efficiency of 7.3% with 78% enhancement over the γ‐phase, showing its potential for future low cost photovoltaic devices.     

Inorganic CsPbI3 Perovskite Coating on PbS Quantum Dot for Highly Efficient and Stable Infrared Light Converting Solar Cells

Solution‐processed colloidal quantum dot (CQD) solar cells harvesting the infrared part of the solar spectrum are especially interesting for future use in semitransparent windows or multilayer solar cells. To improve the device power conversion efficiency (PCE) and stability of the solar cells, surface passivation of the quantum dots is vital in the research of CQD solar cells. Herein, inorganic CsPbI₃ perovskite (CsPbI₃‐P) coating on PbS CQDs with a low‐temperature, solution‐processed approach is reported. The PbS CQD solar cell with CsPbI₃‐P coating gives a high PCE of 10.5% and exhibits remarkable stability both under long‐term constant illumination and storage under ambient conditions. Detailed characterization and analysis reveal improved passivation of the PbS CQDs with the CsPbI₃‐P coating, and the results suggest that the lattice coherence between CsPbI₃‐P and PbS results in epitaxial induced growth of the CsPbI₃‐P coating. The improved passivation significantly diminishes the sub‐bandgap trap‐state assisted recombination, leading to improved charge collection and therefore higher photovoltaic performance. This work therefore provides important insight to improve the CQD passivation by coating with an inorganic perovskite ligand for photovoltaics or other optoelectronic applications.     

Understanding the Role of Cesium and Rubidium Additives in Perovskite Solar Cells: Trap States,Charge Transport,and Recombination

Adding cesium (Cs) and rubidium (Rb) cations to FA_0.83MA_0.17Pb(I_0.83Br_0.17)₃ hybrid lead halide perovskites results in a remarkable improvement in solar cell performance, but the origin of the enhancement has not been fully understood yet. In this work, time‐of‐flight, time‐resolved microwave conductivity, and thermally stimulated current measurements are performed to elucidate the impact of the inorganic cation additives on the trap landscape and charge transport properties within perovskite solar cells. These complementary techniques allow for the assessment of both local features within the perovskite crystals and macroscopic properties of films and full devices. Strikingly, Cs‐incorporation is shown to reduce the trap density and charge recombination rates in the perovskite layer. This is consistent with the significant improvements in the open‐circuit voltage and fill factor of Cs‐containing devices. By comparison, Rb‐addition results in an increased charge carrier mobility, which is accompanied by a minor increase in device efficiency and reduced current–voltage hysteresis. By mixing Cs and Rb in quadruple cation (Cs‐Rb‐FA‐MA) perovskites, the advantages of both inorganic cations can be combined. This study provides valuable insights into the role of these additives in multiple‐cation perovskite solar cells, which are essential for the design of high‐performance devices.     

CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites

The excellent optoelectronic properties demonstrated by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high‐performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead‐halide precursor salts. These adduct‐based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all‐inorganic perovskites such as CsPbI₃. In this work, inorganic perovskite composition CsPbI₃ is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A‐site cation salts. These CsI adducts control nucleation more so than the PbI₂–dimethyl sulfoxide (DMSO) adduct and demonstrate how the A‐site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI–MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.     

Fabrication of Efficient and Stable CsPbI3 Perovskite Solar Cells through Cation Exchange Process

Inorganic lead halide perovskites have attracted attention due to their tolerance to higher processing temperature and higher bandgap suitable for tandem solar cell application. Not only do they improve cell stability and efficiency, they also reveal many interesting and un‐anticipated material qualities. This work reports a simple cation exchange growth (CEG) method for fabricating inorganic high‐quality cesium lead iodide (CsPbI₃) by adding methylammonium iodide (MAI) additive in the precursor. X‐ray diffraction results reveal a multi‐stage film formation process whereby i) MAPbI₃ perovskite first formed that acts as a perovskite template for ii) subsequent ion exchange whereby the MA⁺ ions in the MAPbI₃ are replaced by Cs⁺ (as temperature ramps up) and iii) form g‐phase perovskite CsPbI₃. Optical microscopy, photoluminescence, and electrical characterizations reveal that the CEG process produces high‐quality film with better absorption, uniform and dense film with better interface, lower defects, and better stability. Using the CEG approach, the power conversion efficiency of the best CsPbI₃ solar cell is significantly increased up to 14.1% for the device fabricated using 1.0 m MAI additive. The outcome is beneficial for further improvement of inorganic perovskite solar cells and their application in perovskite‐silicon tandem devices.     

High‐Efficiency CsPbI2Br Perovskite Solar Cells with Dopant‐Free Poly(3‐hexylthiophene) Hole Transporting Layers

CsPbI₂Br is emerging as a promising all‐inorganic material for perovskite solar cells (PSCs) due to its more stable lattice structure and moisture resistance compared to CsPbI₃, although its device performance is still much behind this counterpart. Herein, a preannealing process is developed and systematically investigated to achieve high‐quality CsPbI₂Br films by regulating the nucleation and crystallization of perovskite. The preannealing temperature and time are specifically optimized for a dopant‐free poly(3‐hexylthiophene) (P3HT)‐based device to target dopant‐induced drastic performance degradation for spiro‐OMeTAD‐based devices. The resulting P3HT‐based device exhibits comparable power conversion efficiency (PCE) to spiro‐OMeTAD‐based devices but much enhanced ambient stability with over 95% PCE after 1300 h. A diphenylamine derivative is introduced as a buffer layer to improve the energy‐level mismatch between CsPbI₂Br and P3HT. A record‐high PCE of 15.50% for dopant‐free P3HT‐based CsPbI₂Br PSCs is achieved by alleviating the open‐circuit voltage loss with the buffer layer. These results demonstrate that the preannealing processing together with a suitable buffer layer are applicable strategies for developing dopant‐free P3HT PSCs with high efficiency and stability.     

Highly Stabilized Quantum Dot Ink for Efficient Infrared Light Absorbing Solar Cells

Liquid‐state ligand exchange provides an efficient approach to passivate a quantum dot (QD) surface with small binding species and achieve a QD ink toward scalable QD solar cell (QDSC) production. Herein, experimental studies and theoretical simulations are combined to establish the physical principles of QD surface properties induced charge carrier recombination and collection in QDSCs. Ammonium iodide (AI) is used to thoroughly replace the native oleic acid ligand on the PbS QD surface forming a concentrated QD ink, which has high stability of more than 30 d. The ink can be directly applied for the preparation of a thick QD solid film using a single deposition step method and the QD solid film shows better characteristics compared with that of the film prepared with the traditional PbX₂ (X = I or Br) post‐treated QD ink. Infrared light‐absorbing QDSC devices are fabricated using the PbS‐AI QD ink and the devices give a higher photovoltaic performance compared with the devices fabricated with the traditional PbS‐PbX₂ QD ink. The improved photovoltaic performance in PbS‐AI‐based QDSC is attributed to diminished charge carrier recombination induced by the sub‐bandgap traps in QDs. A theoretical simulation is carried out to atomically link the relationship of QDSC device function with the QD surface properties.     

In Situ Grain Boundary Functionalization for Stable and Efficient Inorganic CsPbI2Br Perovskite Solar Cells

The phase instability and large energy loss are two obstacles to achieve stable and efficient inorganic‐CsPbI_3?xBr_x perovskite solar cells. In this work, stable cubic perovskite (α)‐phase CsPbI₂Br is successfully achieved by Pb(Ac)₂ functioning at the grain boundary under low temperature. Ac^? strongly coordinates with CsPbI₂Br to stabilize the α‐phase and also make the grain size smaller and film uniform by fast nucleation. PbO is formed in situ at the grain boundary by decomposing Pb(Ac)₂ at high‐temperature annealing. The semiconducting PbO effectively passivates the surface states, reduces the interface recombination, and promotes the charge transport in CsPbI₂Br perovskite solar cells. A 12% efficiency and good stability are obtained for in situ PbO‐passivated CsPbI₂Br solar cells, while Pb(Ac)₂‐passivated device exhibits 8.7% performance and the highest stability, much better than the control device with 8.5% performance and inferior stability. This article highlights the extrinsic ionic grain boundary functionalization to achieve stable and efficient inorganic CsPbI_3?xBr_x materials and the devices.     

Structurally Reconstructed CsPbI2Br Perovskite for Highly Stable and Square‐Centimeter All‐Inorganic Perovskite Solar Cells

Although all‐inorganic perovskite solar cells (PSCs) demonstrate high thermal stability, cesium‐lead halide perovskites with high iodine content suffer from poor stability of the black phase (α‐phase). In this study, it is demonstrated that incorporating InCl₃ into the host perovskite lattice helps to inhibit the formation of yellow phase (δ‐phase) perovskite and thereby enhances the long‐term ambient stability. The enhanced stability is achieved by a strategy for the structural reconstruction of CsPbI₂Br perovskite by means of In³⁺ and Cl^? codoping, which gives rise to a significant improvement in the overall spatial symmetry with a closely packed atom arrangement due to the crystal structure transformation from orthorhombic (Pnma) to cubic (Pm‐3m). In addition, a novel thermal radiation heating method that further improves the uniformity of the perovskite thin films is presented. This approach enables the construction of all‐inorganic InCl₃:CsPbI₂Br PSCs with a champion power conversion efficiency of 13.74% for a small‐area device (0.09 cm²) and 11.4% for a large‐area device (1.00 cm²).     

Soft Template‐Controlled Growth of High‐Quality CsPbI3 Films for Efficient and Stable Solar Cells

The unfavorable morphology and inefficient utilization of phase transition reversibility have limited the high‐temperature‐processed inorganic perovskite films in both efficiency and stability. Here, a simple soft template‐controlled growth (STCG) method is reported by introducing (adamantan‐1‐yl)methanammonium to control the nucleation and growth rate of CsPbI₃ crystals, which gives rise to pinhole‐free CsPbI₃ film with a grain size on a micrometer scale. The STCG‐based CsPbI₃ perovskite solar cell exhibits a power conversion efficiency of 16.04% with significantly reduced defect densities and charge recombination. More importantly, an all‐inorganic solar cell with the architecture fluorine‐doped tin oxide (FTO)/NiO_x/STCG‐CsPbI₃/ZnO/indium‐doped tin oxide (ITO) is successfully fabricated to demonstrate its real advantage in thermal stability. By suppressing the inductive effect of defects during the phase transition and utilizing the unique reversibility of the phase transition for the high‐temperature‐processed CsPbI₃ film, the all‐inorganic solar cell retains 90% of its initial efficiency after 3000 h of continuous light soaking and heating.     

Improved photoluminescence stability and defect passivation in SbBr3 post-treated CsPbBr3 quantum dots under ambient conditions

Inorganic cesium lead halide perovskites have evoked wide popularity because of their excellent optoelectronic properties, high photoluminescence (PL) quantum yield (PLQY), and narrowband emission. Here, cesium lead bromide (CsPbBr₃) quantum dots (QDs) were synthesized via the ligand-assisted re-precipitation method. Post-synthesis treatment of CsPbBr₃ QDs using antimony tribromide improved the PL stability and optoelectronic properties of the QDs. In addition, the PLQY of the post-treated sample was enhanced to 91% via post-treatment, and the luminescence observed was maintained for 8 days. The post-synthesis treatment ensured defect passivation and improved the stability of CsPbBr₃ perovskite QDs. High-resolution transmission electron microscopy revealed the presence of more ordered, uniform-sized CsPbBr₃ QDs after post-synthesis treatment, and the uniformity of the sample improved as the day passed. The formation of a mixed crystal phase was observed from X-ray diffraction in both as-synthesized, as well as post-treated QDs samples with the possibility of a polycrystalline nature in the post-treated CsPbBr₃ QDs as per the selected area electron diffraction pattern. The X-ray photoelectron spectroscopy spectra confirmed the presence of antimony and the possibility of defect passivation in the post-treated samples. These QDs can act as potential candidates in various optoelectronic applications such as photodetectors and light-emitting diodes due to their high PLQY and longer lifetime.     

A Novel Anion Doping for Stable CsPbI2Br Perovskite Solar Cells with an Efficiency of 15.56% and an Open Circuit Voltage of 1.30 V

The Cs‐based inorganic perovskite solar cells (PSCs), such as CsPbI₂Br, have made a striking breakthrough with power conversion efficiency (PCE) over 16% and potential to be used as top cells for tandem devices. Herein, I^? is partially replaced with the acetate anion (Ac^?) in the CsPbI₂Br framework, producing multiple benefits. The Ac^? doping can change the morphology, electronic properties, and band structure of the host CsPbI₂Br film. The obtained CsPbI_2?x Br(Ac)_x perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI₂Br films. Interestingly, the CsPbI_2?x Br(Ac)_x PSCs exhibit a maximum PCE of 15.56% and an ultrahigh open circuit voltage (V_oc) of 1.30 V without sacrificing photocurrent. Notably, such a remarkable V_oc is among the highest values of the previously reported CsPbI₂Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI_2?x Br(Ac)_x PSCs exhibit high reproducibility and good stability. The stable CsPbI_2?x Br(Ac)_x PSCs with high V_oc and PCE are desirable for tandem solar cell applications.     

A Low-Temperature Additive-Involved Leaching Method for Highly Efficient Inorganic Perovskite Solar Cells

Inorganic CsPbI₃ perovskite with an optical bandgap ranging from 1.67 to 1.75 eV is a promising light-harvesting material as a top cell in tandem solar cells, but its high fabrication temperature can damage the middle layers or the bottom subcells. Here, an additive-involved leaching method to fabricate CsPbI₃ perovskite films is demonstrated, which can decrease the preparation temperature to 100 °C. The CsPbI₃ perovskite films with high crystallinity are achieved by a solution assisted reaction between DMAPbI₃ and Cs₄PbI₆ with the leaching of DMA⁺, Cs⁺, and I⁻. The as-prepared CsPbI₃ perovskite films exhibit much superior stability compared to their high-temperature counterparts. As a result, a power conversion efficiency of over 16% is obtained, and the unencapsulated device maintains over 93% of the initial efficiency after aging for 30 days in air with a relative humidity of 10%.     

Inorganic CsPb1−xSnxIBr2 for Efficient Wide‐Bandgap Perovskite Solar Cells

Recently, the stability of organic–inorganic perovskite thin films under thermal, photo, and moisture stresses has become a major concern for further commercialization due to the high volatility of the organic cations in the prototype perovskite composition (CH₃NH₃PbI₃). All inorganic cesium (Cs) based perovskite is an alternative to avoid the release or decomposition of organic cations. Moreover, substituting Pb with Sn in the organic–inorganic lead halide perovskites has been demonstrated to narrow the bandgap to 1.2–1.4 eV for high‐performance perovskite solar cells. In this work, a series of CsPb_1?xSn_xIBr₂ perovskite alloys via one‐step antisolvent method is demonstrated. These perovskite films present tunable bandgaps from 2.04 to 1.64 eV. Consequently, the CsPb_0.75Sn_0.25IBr₂ with homogeneous and densely crystallized morphology shows a remarkable power conversion efficiency of 11.53% and a high V_oc of 1.21 V with a much improved phase stability and illumination stability. This work provides a possibility for designing and synthesizing novel inorganic halide perovskites as the next generation of photovoltaic materials.     

Stabilizing the Efficiency Beyond 20% with a Mixed Cation Perovskite Solar Cell Fabricated in Ambient Air under Controlled Humidity

Perovskite solar cells have evolved to have compatible high efficiency and stability by employing mixed cation/halide type perovskite crystals as pinhole‐free large grain absorbers. The cesium (Cs)–formamidium–methylammonium triple cation‐based perovskite device fabricated in a glove box enables reproducible high‐voltage performance. This study explores the method to reproduce stable and high power conversion efficiency (PCE) of a triple cation perovskite prepared using a one‐step solution deposition and low‐temperature annealing fully conducted in controlled ambient humidity conditions. Optimizing the perovskite grain size by Cs concentration and solution processes, a route is created to obtain highly uniform, pinhole‐free large grain perovskite films that work with reproducible PCE up to 20.8% and high preservation stability without cell encapsulation for more than 18 weeks. This study further investigates the light intensity characteristics of open‐circuit voltage (V_oc) of small (5 × 5 mm², PCE > 20%) and large (10 × 10 mm², PCE of 18%) devices. Intensity dependence of V_oc shows an ideality factor in the range of 1.7‐1.9 for both devices, implying that the triple cation perovskite involves trap‐assisted recombination loss at the hetero junction interfaces that influences V_oc. Despite relatively high ideality factor, perovskite device is capable of supplying high power conversion efficiency under low light intensity (0.01 Sun) whereas maintaining V_oc over 0.9 V.     

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

All‐inorganic cesium lead halide (CsPbX₃) perovskites have emerged as promising photovoltaic materials owing to their superior thermal stability compared to traditional organic–inorganic hybrid counterparts. However, the CsPbX₃ perovskites generally need to be prepared at high‐temperature, which restricts their application in multilayer or flexible solar cells. Herein, the formation of CsPbX₃ perovskites at room‐temperature (RT) induced by dimethylsulphoxide (DMSO) coordination is reported. It is further found that a RT solvent (DMSO) annealing (RTSA) treatment is valid to control the perovskite crystallization dynamics, leading to uniform and void‐free films, and consequently a maximum power conversion efficiency (PCE) of 6.4% in the device indium tin oxide (ITO)/NiO _x /RT‐CsPbI₂Br/C₆₀/Bathocuproine (BCP)/Ag, which is, as far as it is known, the first report of RT solution‐processed CsPbX₃‐based perovskite solar cells (PSCs). Moreover, the efficiency can be boosted up to 10.4% by postannealing the RTSA‐treated perovskite film at an optimal temperature of 120 °C. Profiting from the moderate temperature, flexible PSCs are also demonstrated with a maximum PCE of 7.3% for the first time. These results may stimulate further development of all‐inorganic CsPbX₃ perovskites and their application in flexible electronics.     

Pb‐Reduced CsPb0.9Zn0.1I2Br Thin Films for Efficient Perovskite Solar Cells

Fabrication of efficient Pb reduced inorganic CsPbI₂Br perovskite solar cells (PSC) are an important part of environment‐friendly perovskite technology. In this work, 10% Pb reduction in CsPb_0.9Zn_0.1I₂Br promotes the efficiency of PSCs to 13.6% (AM1.5, 1sun), much higher than the 11.8% of the pure CsPbI₂Br solar cell. Zn²⁺ has stronger interaction with the anions to manipulate crystal growth, resulting in size‐enlarged crystallite with enhanced growth orientation. Moreover, the grain boundaries (GBs) are passivated by the Cs‐Zn‐I/Br compound. The high quality CsPb_0.9Zn_0.1I₂Br greatly diminishes the GB trap states and facilitates the charge transport. Furthermore, the Zn4s‐I5p states slightly reduce the energy bandgap, accounting for the wider solar spectrum absorption. Both the crystalline morphology and energy state change benefit the device performance. This work highlights a nontoxic and stable Pb reduction method to achieve efficient inorganic PSCs.