Small Molecule–Polymer Composite Hole-Transporting Layer for Highly Efficient and Stable Perovskite Solar Cells

Abstract

Effective and stable hole-transporting materials (HTMs) are necessary for obtaining excellent planar perovskite solar cells (PSCs). Herein, we reported a solution-processed composite HTM consisting of a polymer poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and a small-molecule copper phthalocyanine-3,4',4″,4‴-tetrasulfonated acid tetrasodium salt (TS-CuPc) with optimized doping ratios. The composite HTM is crucial for not only enhancing the hole transport and extraction but also improving the perovskite crystallization. In addition, the composite HTM can weaken the indium tin oxide erosion by reducing the acidity and increasing the dispersibility of the PEDOT:PSS aqueous dispersion via incorporating suitable TS-CuPc. Consequently, a highly efficient device was fabricated with a power conversion efficiency (PCE) of 17.29%. Its short-circuit current (J) is 22.23 mA/cm, and its open-circuit voltage (V) is 1.01 V. Meanwhile, it exhibited a higher fill factor (FF) of 77% and improved cell stability. The developed composite HTM provides a good potential anode interfacial layer for fabricating outstanding PSCs.

Doped Copper Phthalocyanine via an Aqueous Solution Process for Normal and Inverted Perovskite Solar Cells

“…Whatever the structure may be inverted PSCs or a normal PSCs, hole‐transporting materials (HTMs) undertake the responsibility of extracting and collecting the photon‐generated holes from the perovskite active layer . Poly(3,4‐ethylene dioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS), CuI, NiO, CuO x and copper thiocyanate (CuSCN), germanium dioxide (GeO 2 ), graphene oxide (GO), and poly(triarylamine) (PTAA), 2,2′,7,7′‐tetrakis‐( N , N ‐di‐ p ‐methoxyphenylamine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD), and poly‐3‐hexylthiophene (P3HT), have been employed as HTMs in p–i–n and n–i–p PSCs, respectively. However, these reported HTMs more or less are enslaved to the disadvantages of high cost, thermal and chemical instability, acidic nature, and low mobility and/or conductivity, which seriously hinders their potential applications in commercialization.…”

Review on methods for improving the thermal and ambient stability of perovskite solar cells

“…The double-layered structure avoids this defect while isolating ITO and PEDOT:PSS. In addition, CuPc/PEDOT:PSS composite HTLs 87 and CuI/PEDOT:PSS double layer HTLs 88 with an inverted structure have also been proposed. The performance of cells fabricated with these layers is improved compared with that of a single-layer HTL.…”

Highly Efficient and Stable Perovskite Solar Cells Using a Dopant‐Free Inexpensive Small Molecule as the Hole‐Transporting Material

“…Realizing that PSCs with Spiro‐MeOTAD as the HTL are not going to be commercially viable, researchers around the world have devoted tremendous efforts toward the development of new organic HTL materials . However, the top performing HTL materials reported so far have complicated structures involving multistep syntheses and are expensive . Most of these materials do not have sufficient hole mobility and thus still require doping to achieve sufficient conductivity .…”

“…However, the top performing HTL materials reported so far have complicated structures involving multistep syntheses and are expensive . Most of these materials do not have sufficient hole mobility and thus still require doping to achieve sufficient conductivity . They also contain multiple nitrogen and/or oxygen atoms, which typically attract moisture, detrimental to device stability .…”