A stable perovskite heterojunction was constructed for inverted solar cells through surface sulfidation of lead (Pb)–rich perovskite films. The formed lead-sulfur (Pb-S) bonds upshifted the Fermi level at the perovskite interface and induced an extra back-surface field for electron extraction. The resulting inverted devices exhibited a power conversion efficiency (PCE) >24% with a high open-circuit voltage of 1.19 volts, corresponding to a low voltage loss of 0.36 volts. The strong Pb-S bonds could stabilize perovskite heterojunctions and strengthen underlying perovskite structures that have a similar crystal lattice. Devices with surface sulfidation retained more than 90% of the initial PCE after aging at 85°C for 2200 hours or operating at the maximum power point under continuous illumination for 1000 hours at 55° ± 5°C.

No abstract

Hybrid halide perovskite based on CH3NH3PbI3 and related materials has emerged as the most exciting development in the next generation photovoltaic technologies. There is still requirement for an effective method to establish a relationship between the charge transfer behaviors and photovoltaic properties. This study presents Kelvin probe force microscopy and conductive atomic force microscopy measurements of versatile perovskite films that participate in the formation of different heterojunctions, exploring local current, contact potential difference (CPD), and charge activities at the nanoscale. By comparing the values of CPD and current of these perovskite films in dark and under illumination, the charge transfer behaviors are locally illustrated, suggesting that the perovskite roles in these heterojunctions are strictly dependent on the contact layers. Furthermore, the average difference (ΔV) of the CPD values obtained in dark and under illumination for each heterojunction can be set to analyze the efficacy of the perovskite/contact layer interfaces. The ΔV polarity is related to the type of charge carrier (hole or electron), while the ΔV magnitude is related to the number of charge carrier. These results emphasize the importance of understanding of these heterojunction systems that could guide the design and optimization of the photovoltaic configuration.

No abstract

The quality of perovskite film is an important factor influencing the photovoltaic properties of solar cells, which is greatly affected by deposition methods. Here, Lewis acid−base interaction-induced porous PbI 2 film is obtained by 4-tert-butylpyridine (TBP) vapor treatment method. X-ray diffraction, Raman spectroscopy, and Fourier transform infrared characteristics indicate that a new complex including both TBP and PbI 2 molecules was formed by Lewis acid−base reaction. A continuous, uniform, and PbI 2 -free perovskite film with large grains was obtained from the porous PbI 2 reacted completely with CH 3 NH 3 I. As a result, a promising power conversion efficiency of ∼18% is achieved in planarheterojunction perovskite solar cells. Furthermore, via controlling the vapor treatment time, the porosity and thickness of PbI 2 film can be readily adjusted, and the unexpected mesoporous perovskite film was first fabricated. Our work demonstrates the preparation of porous PbI 2 films by Lewis base vapor treatment for highly efficient planar perovskite solar cells.