A Review on Solution‐Processable Dopant‐Free Small Molecules as Hole‐Transporting Materials for Efficient Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) based on conventional hole‐transporting materials (HTMs) have achieved power conversion efficiencies comparable to those of typical inorganic solar cells; however, the dopants used to increase the hole mobility or the film‐forming ability impart these devices with a poor long‐term stability, blocking the industrial commercialization of PSCs. As an alternative, HTMs without any dopants are explored. Herein, dopant‐free small molecular HTMs (SM‐HTMs) are reviewed and the performance based on the analyses of their molecular structures are evaluated. A summary of the designing principle and an outlook of the development of highly efficient SM‐HTMs are presented.

Exploration of conjugated π-bridge units in N,N-bis(4-methoxyphenyl)naphthalen-2-amine derivative-based hole transporting materials for perovskite solar cell applications: a DFT and experimental investigation

“…8,9 Therein, the typical HTM of 2,2 0 ,7,7 0 -tetrakis (N,N-di-p-methoxyphenylamino)-9,9 0 -spirobiuorene (Spiro-OMeTAD) in PSC device applications can yield high PCE. 10,11 However, the core conguration of spiro in Spiro-OMeTAD with the complexity and high cost of synthesis limited the widespread application. 12,13 In addition, the hole mobility of the HTMs should be as high as possible, but many organic HTMs including Spiro-OMeTAD, polytriarylamine (PTAA), benzon[1,2b:3,4-b 0 :5,6-b 00 ] trithiophene have a relatively low hole mobility of about 10 À5 cm 2 V À1 s À1 order of magnitude.…”

Bithieno Thiophene-Based Small Molecules for Application as Donor Materials for Organic Solar Cells and Hole Transport Materials for Perovskite Solar Cells

“…With a root-mean-square (rms) roughness of 0.44 nm, the MPA-BTTI film had a considerably smoother surface. 26 Due to the low hysteresis, improved thermal stability, and long-term stability, the MPA-BTTI-based dopant-free PSCs achieve a phenomenal efficiency of 21.17 percent. 27 The MPA-BTTI’s film morphology and well-aligned energy levels are credited with this accomplishment.…”

“…Due to the more expanded and conjugated system, MPA-BTTI adopted an H-aggregation style, resulting in more efficient charge transportation and better hole mobility. With a root-mean-square (rms) roughness of 0.44 nm, the MPA-BTTI film had a considerably smoother surface . Due to the low hysteresis, improved thermal stability, and long-term stability, the MPA-BTTI-based dopant-free PSCs achieve a phenomenal efficiency of 21.17 percent .…”

Efficient and Stable Mesoscopic Perovskite Solar Cells Using a Dopant‐Free D–A Copolymer Hole‐Transporting Layer

“…[1][2][3][4][5][6][7] Due to their excellent optoelectronic properties such as high absorption and great mobility, bandgap tunability, low-cost processing, and ease of fabrication, they have been the most favorable absorber layer for the fabrication of efficient perovskite solar cells (PSCs). [8][9][10][11][12][13][14] Over the past decade, extensive efforts on interface and compositional engineering, surface passivation, and band alignment engineering have been devoted, resulted in a certified power conversion efficiency (PCE) of 25.5%. [15][16][17][18] In addition to PCE, device stability plays a key role for the commercialization of the PSCs.…”