Perovskite Solar Cells Based on Polymerized Chlorophyll Films as Environmentally Friendly Hole‐Transporting Layers

Abstract

Hole‐transporting layers (HTLs) play a crucial role in the performance of inverted, p‐i‐n perovskite solar cells (PSCs). Chlorophylls (Chls) are naturally abundant organic photoconductors on earth, with good charge carrier mobility and appropriate Fermi energy levels that make them promising candidates for use in photovoltaic devices. However, Chls films prepared using the solution method exhibit lower carrier mobility compared to other organic polymer films, which limits their application in PSCs. To address this issue, Chls molecules are chemically linked to reduce the charge transfer barrier, thus the transfer of charges between molecules is transformed to intramolecular charge transfer. This study synthesizes and characterizes two polymerized Chl films, PolyCuChl and PolyNiChl, as HTLs of CH3NH3PbI3‐based PSCs. PSCs based on the electrochemical polymerization of PolyChl HTLs demonstrate an enhanced power conversion efficiency (PCE) of up to 19.0%, which is the highest efficiency among devices based on Chl materials. Furthermore, these devices demonstrated exceptional long‐term stability. These results highlight the potential of polymerized Chl films as a viable alternative to conventional HTLs in PSCs. The approach utilizes abundant, environmentally friendly, and versatile Chl derivatives, and can be extended to develop next‐generation HTL materials for improved PSC performance.

Recent Research Progress and Perspectives on Porphyrin and Phthalocyanine Analogues for Perovskite Solar Cell Applications

“…Further advancing our research, we synthesized a series of five bacteriochlorophyll a derivatives, each modified at the C17-propionate position, to explore their potential for forming J-type aggregates as HTLs in PSCs. 51 The modifications to the C17-propionate residues minimally influenced the core electrochemical characteristics of the dye, such as the electronic absorption spectra and energy levels. However, alterations in lipophilicity and hydrophobicity due to these modifications significantly affected the solubility of the derivatives, which in turn impacted their surface morphologies.…”

“…(h) Molecular Structure of CuChl and NiChl and schematic diagram of the electrochemical polymerization device. This figure was reproduced with permission from ref . Copyright 2023 Wiley.…”

“…To overcome the inherent challenge of low carrier mobility in Chl thin films prepared by solution methods, our research team developed two novel polymerized Chl films: PolyCuChl and PolyNiChl . These films serve as undoped HTLs in CH 3 NH 3 PbI 3 -based PSCs.…”

Porphyrin-Based Hole-Transporting Materials for Perovskite Solar Cells: Boosting Performance with Smart Synthesis

“…The small PCE of Zn-Por3-based PSCs has been attributed to the deeper HOMO level that produces a small energy gap between Zn-Por3 and MAPbI 10a) for inverted based-MAPbI 3 PSC are the best outcomes reported with chlorophyll derivatives. 46 The authors selected methyl pyropheophorbide-a to prepare CuChl and NiChl monomers by metalation with adequate…”

“…Now, the exploration of PolyCuChl and PolyNiChl films obtained via the electrochemical polymerization of CuChl and NiChl ( Figure 10 a) for inverted based-MAPbI 3 PSC are the best outcomes reported with chlorophyll derivatives. 46 The authors selected methyl pyropheophorbide- a to prepare CuChl and NiChl monomers by metalation with adequate metal(II) acetate salt. Posteriorly, coupling of the peripheral vinyl group via electrochemical polymerization on the FTO glass afforded PolyCuChl and PolyNiChl .…”