A Coplanar π‐Extended Quinoxaline Based Hole‐Transporting Material Enabling over 21 % Efficiency for Dopant‐Free Perovskite Solar Cells

Abstract

Developing dopant‐free hole transporting materials (HTMs) is of vital importance for addressing the notorious stability issue of perovskite solar cells (PSCs). However, efficient dopant‐free HTMs are scarce. Herein, we improve the performance of dopant‐free HTMs featuring with a quinoxaline core via rational π‐extension. Upon incorporating rotatable or chemically fixed thienyl substitutes on the pyrazine ring, the resulting molecular HTMs TQ3 and TQ4 show completely different molecular arrangement as well as charge transporting capabilities. Comparing with TQ3, the coplanar π‐extended quinoxaline based TQ4 endows enriched intermolecular interactions and stronger π–π stacking, thus achieving a higher hole mobility of 2.08×10−4 cm2 V−1 s−1. It also shows matched energy levels and high thermal stability for application in PSCs. Planar n‐i‐p structured PSCs employing dopant‐free TQ4 as HTM exhibits power conversion efficiency (PCE) over 21 % with excellent long‐term stability.

Hydrogen-Bonded Dopant-Free Hole Transport Material Enables Efficient and Stable Inverted Perovskite Solar Cells

“…38 In this Page 10 of 24 CCS Chemistry work, the charge transport properties of both films with and without Boc groups were evaluated by utilizing the space-charge-limited-current (SCLC) method. 39 The dark I-V characteristics of the hole-only devices with configuration 'ITO/PEDOT:PSS/hole transport layer (HTL)/ Ag' were evaluated (Figure 2e). The hole mobilities were extracted by the Mott-Gurney Law (1):…”

Molecular Engineering of Polymeric Hole-Transporting Materials for Efficient and Stable Perovskite Solar Cells

“…Unfortunately, these works were still under the molecular structure framework of traditional controversial spiro-OMeTAD or unavoidable to dopants. Thus, researchers have been putting efforts into synthesizing new dopant-free small organic molecules − and polymers − with novel structures by different strategies. One tactic is to incorporate thiophene or its derivatives, thereby reconstructing the structures of HTMs to ameliorate the optoelectronic properties, such as energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), mobility, and absorption range.…”

Regulation of hole transport layer for perovskite quantum dot light-emitting diodes

“…Owing to their tunable direct bandgap, high optical absorption coefficient, long carrier diffusion length and high defect tolerance, perovskites have been widely attempted in various optoelectronic applications, such as solar cells, light-emitting diodes, lasers and optical detectors. [1][2][3][4][5][6][7] Peroveskite quantum dots have been widely reported as emissive materials in LEDs because of their high quantum yield, good monochromaticity (FWHM~20nm), adjustable color and other advantages. At present, the highest EQEs of three primary RGB colors have exceeded 20%, [8] for red and green and 10% for bule [9] .…”