Molecularly Engineered Phthalocyanines as Hole‐Transporting Materials in Perovskite Solar Cells Reaching Power Conversion Efficiency of 17.5%

Abstract

intense panchromatic absorption [4] and high charge carrier mobilities. [5] In addition, their band gap can be easily tuned by simple variation of their ionic composition. [6] For example, a mixed-ion perovskite obtained as a mixture of formamidinium (FA) lead iodide and methy lammonium (MA) lead bromide, [FAPbI 3 ] 0.85 [MAPbBr 3 ] 0.15 , delivered the best to date energy conversion efficiencies of over 21% and revealed promising stability and reproducibility. [7-9] All the above mentioned, together with the ambipolar charge transport characteristics of perovskites, [10] are exceptional properties behind the high efficiency reported in literature. However, highly efficient PSCs are mostly achieved when sandwiching the perovskite film between an electron-transport layer (ETM, n-type) and a hole-transport layer (HTM, p-type), to enhance the selective blocking and extraction of charges into the external circuit. In this connection, using mesoporous or planar metal oxide ETM, such as TiO 2 , delivered the best results. [11] In terms of HTM, small molecules and polymers have shown impressive performances, being so far 2,2′,7,7′-tetrakis(N,N-dip -methoxyphenylamin e)-9,9′-spirobifluorene (Spiro-OMeTAD) [12] and poly(triaryl-amine) (PTAA) [13]

Regioregular Phthalocyanines Substituted with Bulky Donors at Non‐Peripheral Positions

“…Recently, Torres and Nazeeruddin et al. reported a high PCE value of 15.5 % by using ZnPcs substituted with 5‐hexyl‐2,2′‐bisthiophenes as HTMs in PSCs . They found that the π‐π stacking of ZnPcs in the HTM layer greatly enhanced the PCE values of PSCs.…”

Interfacial Engineering of Perovskite Solar Cells by Employing a Hydrophobic Copper Phthalocyanine Derivative as Hole‐Transporting Material with Improved Performance and Stability

“…[9,[18][19][20] However,t he solubility of CuPc in common organic solvents is rather poor.T herefore, it hast ob et hermally evaporated under high vacuum in these PSC devices,w hich results in additional production costs. [23] Triphenylamine (TPA) is aw ell-known electron donora nd has been widely used in small-molecule-based HTMs. [21,22] Very recently,m olecularly engineered zinc phthalocyanines (ZnPcs) have been developed as solutionprocessable HTMs in PSCs with an maximum PCE of 17.5 %.…”

Low‐Cost Perovskite Solar Cells Employing Dimethoxydiphenylamine‐Substituted Bistricyclic Aromatic Enes as Hole Transport Materials

“…On the other hand, to ensure low‐cost perovskite solar cell manufacturing, an ideal HTM candidate has to be easily affordable by simple synthetic schemes with minimized number of steps and easy workup and purification procedures for cost‐effective upscale. To date, molecular spiro‐type HTMs spiro‐OMeTAD [2,2′,7,7′‐tetrakis‐( N , N ‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene], FDT {2′,7′‐bis[bis(4‐methoxyphenyl)amino]spiro[cyclopenta(2,1‐b:3,4‐b′)dithiophene‐4,9′‐fluorene]}, and DDOF {2,2’,7,7′‐tetrakis‐( N , N ′‐di‐4‐methoxyphenylamine)dispiro‐[fluorene‐9,4′‐dithieno(3,2‐c:2′,3′‐e)oxepine‐6′,9′′‐fluorene]} reached the highest reported values over 19 % along with various other small‐molecule HTMs based on paracyclophane, truxene, benzotrithiophene, fluorene, carbazole, triazatruxene, anthratetrathiophene, phthalocyanine, indoloindole, and phenothiazine, successfully reaching comparably high photovoltaic performance. However, there are still only very few examples with a particular emphasis on low‐cost and highly efficient molecular HTMs such as spiroxanthene‐, fluorene‐, carbazole‐, and bifluorene‐based compounds including recently reported KR216 based on bifluorenylidene, and obtained by straightforward strategies showing that proper molecular engineering may be very fruitful toward low‐cost commercial solar cell application.…”