Stable Perovskite Solar Cells Using Molecularly Engineered Functionalized Oligothiophenes as Low‐Cost Hole‐Transporting Materials

Abstract

alternative to the existing conventional energy sources. [1] Organometal-halide perovskites show exceptional panchromatic light harvesting ability, high molar extinction coefficient, high charge carrier mobilities, and long electron-hole diffusion lengths. Further, the versatility and tunable electronic properties of perovskites are beneficial for realizing higher photovoltaic performance reaching over 25%. [2][3][4][5] However, low charge extraction and poor stability of the metal-halide perovskite limit their credentials in large-scale applications.To overcome these limitations, p-type semiconducting materials, also known as hole-transporting materials (HTMs), were sandwiched between perovskite and metal electrode. HTMs play a vital role in PSCs to extract and transfer the positive charges and thus achieve high efficiency. [6][7][8][9][10] They can be classified as inorganic, [11] polymeric, [12] and small molecular organic HTMs. [13,14] Among them, small molecular HTMs are superior to other counterparts owing to their structural diversity, well-defined molecular Triarylamine-substituted bithiophene (BT-4D), terthiophene (TT-4D), and quarterthiophene (QT-4D) small molecules are synthesized and used as low-cost hole-transporting materials (HTMs) for perovskite solar cells (PSCs). The optoelectronic, electrochemical, and thermal properties of the compounds are investigated systematically. The BT-4D, TT-4D, and QT-4D compounds exhibit thermal decomposition temperature over 400 °C. The n-i-p configured perovskite solar cells (PSCs) fabricated with BT-4D as HTM show the maximum power conversion efficiency (PCE) of 19.34% owing to its better hole-extracting properties and film formation compared to TT-4D and QT-4D, which exhibit PCE of 17% and 16%, respectively. Importantly, PSCs using BT-4D demonstrate exceptional stability by retaining 98% of its initial PCE after 1186 h of continuous 1 sun illumination. The remarkable long-term stability and facile synthetic procedure of BT-4D show a great promise for efficient, stable, and low-cost HTMs for PSCs for commercial applications.

Fused thiophene based materials for organic thin‐film transistors

“…[ 66 ] Later, bithiophene‐based (BT‐4D; 106 ) and carbazole‐based (Car [ 2,3 ] ; 107 ) molecules have been developed as HTMs and exhibited the performance of 19.34% and 19.23%, respectively, in the n‐i‐p configured Pb‐based perovskite solar cells (PSCs). [ 67 ] It is an important to note that PSCs using BT‐4D molecule demonstrate exceptional stability by retaining 98% of its initial PCE after 1,186 hr of continuous 1 sun illumination. Recently, we have designed and developed efficient HTMs, DImBT‐4D ( 108) and DPTP‐4D ( 109), which deliver PCEs of 20.11% and 20.18%, respectively, in Pb‐based PSC.…”

Enhancing Hole Transport of Quantum‐Dot Light‐Emitting Diodes by a Cruciform Oligothiophene for Effective p‐Type Doping

“…Unlike polymeric dopants, oligomeric materials have a welldefined chemical structure, precise molecular weight, and high purity. In addition, oligothiophene materials have high electron density and charge carrier mobility, [26,27] making them suitable as dopants for the HTLs. [28,29] Not to mention, oligothiophenes with various structures offer a family of derivatives to study tailoredmade motifs for promoting the hole mobility of QLEDs.…”

A dopant-free donor–acceptor type semi-crystalline polymeric hole transporting material for superdurable perovskite solar cells

“…3 To date, highly efficient PSCs with PCEs exceeding 20% have been realized in n-i-p device architectures, mostly using 2,2 0 ,7,7 0 -tetrakis(N,N 0 -di-p-methoxyphenylamine)-9,9 0 -spirobi-uorene (spiro-OMeTAD). 4 However, spiro-OMeTAD has a bulky spiro-core and twisted arylamine units, which are not efficient molecular structures for tight packing and intermolecular interactions. 5 Chemical dopants such as a Li-based salt (Li-TFSI) and 4-tert-butylpyridine (4-tBP) are essentially required to overcome the poor electrical properties.…”

“…3 To date, highly efficient PSCs with PCEs exceeding 20% have been realized in n–i–p device architectures, mostly using 2,2′,7,7′-tetrakis( N , N ′-di- p -methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). 4…”