Pyrene-based hole transport materials for efficient perovskite solar cells

In the past few years, perovskite solar cells (PSCs) have gained a lot of attention and become a well-known topic in solar studies due to their lower manufacturing costs and improved efficiencies. Previously utilized hole transport materials (HTMs), such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] and 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene, are challenging due to their high price, complicated synthesis, limited carrier mobility, and poor device stability. Developing HTMs for PSCs that are inexpensive and high-performance has gained much interest. Currently, many HTMs of organic molecules are used to improve photovoltaic qualities and reduce synthesis costs. Effectively using HTMs is essential for producing the best photovoltaic efficiency in PSCs because they are essential in extracting and transporting charge carriers. Pyrene-based HTMs have excellent device performance, chemical stability, and photovoltaic qualities compared to the other organic moieties. The significant developments made in pyrene-based HTMs over the past five years are reported herein. This review analyzed the relationship between the molecular structure, hole mobility, highest occupied molecular orbital-lowest unoccupied molecular orbital energy levels, power conversion efficiency (PCE), and energy band gap of pyrene-based HTMs. It was revealed that PSC devices fabricated with pyrene-based HTMs have attained a PCE greater than 22%. It is hoped that this review will encourage more researchers to develop HTMs that have good performance, low cost, and high device stability.