Lead(II) Propionate Additive and a Dopant-Free Polymer Hole Transport Material for CsPbI₂Br Perovskite Solar Cells

Abstract

All-inorganic perovskites (CsPbI3 and CsPbI2Br), owing to their greater thermal stability compared to organic–inorganic hybrid perovskites, are becoming popular in perovskite photovoltaics, but the problem that remains with CsPbI2Br (or CsPbI3) is the humidity-assisted phase transformation. Herein, we report on the formation of CsPbI2Br α-phase and improvement of its phase stability under ambient atmosphere (20–30% relative humidity) by Pb­(II) propionate additive in the CsPbI2Br precursor. Solar cells employing a CsPbI2Br film with an optimum concentration of the additive (1 mol %) and a donor–acceptor type polymer (synthesized by us) as dopant-free hole transport material that has a better energy level matching with CsPbI2Br (compared to other polymers like P3HT, PTAA, and asy-PBTBDT) work with a champion power conversion cell efficiency of 14.58%. A continuous increase in the open-circuit voltage, reaching 1.36 V for 5 mol % Pb­(II) propionate, indicates a remarkable defect-passivation effect by the additive.

One‐Source Strategy Boosting Dopant‐Free Hole Transporting Layers for Highly Efficient and Stable CsPbI2Br Perovskite Solar Cells

“…[ 25 ] A high photostability with an efficiency drop of less than 10% was realized under continuous 1 sun equivalent illumination for 400 h. Similar behavior was achieved by adopting other hydrophobic PDMs as the HTL, such as PBDB‐T‐Si, [ 26 ] poly[[5,6‐difluoro‐2‐(2‐hexyldecyl)‐2H‐benzotriazole‐4,7‐diyl]‐2,5‐thiophenediyl[4,8‐bis[5‐(tripropylsilyl)‐2‐thienyl]benzo[1,2‐b:4,5‐b']dithiophene‐2,6‐diyl]‐2,5‐thiophenediyl] (J71), [ 27 ] and poly[(dithieno[3,2‐b:2′,3′‐d]silolethieno[3,4‐c]‐pyrrole‐4,6‐dione)‐random‐(2,2′‐bithiophenethieno[3,4‐c]‐pyrrole‐4,6‐dione)] (poly(DTSTPD‐r‐BThTPD)). [ 28 ] Although the dopant‐free strategy improves device stability, PCEs still encounter insurmountable bottlenecks toward high values. Therefore, it is crucial to fabricate high‐quality CsPbI 2 Br films and develop dopant‐free HTMs at the same time, and to form good electronic contact between them.…”

Single- or double A-site cations in A3Bi2I9 bismuth perovskites: What is the suitable choice?

“…In addition to this, the development of inorganic perovskites (e.g. : CsPb(I x Br 1−x ) 3 ) has garnered significant attention because of their inorganic nature, high thermal stability up to 350 °C, and wide E g which is useful for tandem devices [18,19]. To date, most of the top-performing 2…”

Implementing Dopant-Free Hole-Transporting Layers and Metal-Incorporated CsPbI2Br for Stable All-Inorganic Perovskite Solar Cells

“…To address this economical impairment, low-cost, dopant-free HTLs which are also hydrophobic are required. 37 − 39 For the case of all-inorganic CsPbI 2 Br-based PSC, the use of poly[(dithieno[3,2-b:2′,3′-d]silolethieno[3,4- c ]pyrrole-4,6-dione)-random-(2,2′-bithiophenethieno[3,4- c ]pyrrole-4,6-dione)] (poly(DTSTPD-r-BThTPD) 40 and a dopant-free donor–acceptor polymer poly(DTSTPD-r-BThTPD) have demonstrated good PCE. 41 However, the synthesis of poly(DTSTPD-r-BThTPD) is tedious and the issue of cost still remains.…”

“…(f) Distribution of PCE based on different dopant-free HTLs reported to date. Data has been extracted from refs ( 40 , 43 , 65 , and 65 ).…”