Organic Hole-Transport Materials for Perovskite Solar Cells

Research on perovskite solar cells (PSCs) has undergone dramatic development since the first cells were reported in 2009, and the past decade has witnessed a significant breakthrough on their power conversion efficiencies (PCEs) from 3.8% to 25%. However, the large-scale industrialization of PSCs is still far from an easy task, due to the scarcity of high-performance and low-cost organic hole-transport materials (HTMs). Thus, the development of new generation HTMs is highly desired. The studies in this thesis aim at developing novel, inexpensive and easily synthesizable organic HTMs for application in efficient PSCs. A series of HTMs from small molecules to polymers, from doped to dopant-free were designed, synthesized and tested, to further improve the stability and reduce the cost. In Chapter 1 and Chapter 2, a brief introduction to PSCs, HTMs as well as the characterization methods used in this thesis are presented. In Chapter 3 and Chapter 4, the design and synthesis of a series of carbazole- based and spiro[fluorene-9,9'-xanthene] (SFX)-based HTMs is described. For these HTMs, the influence of substitution position, linking topology, pendant group and molecular size on the optical and electronic properties was systematically investigated, as well as their performance in solar cells. In Chapter 5, two small molecular HTMs based on extended SFX skeletons were introduced for the application in dopant-free PSCs. The effect of the extended conjugation core unit and molecular size on the electrochemical and optical properties, hole mobility, conductivity, molecular packing and PSC performance was studied in detail. In Chapter 6, a crosslinked SFX-based polymer was designed and synthesized as an efficient, low-cost, dopant-free HTM for conventional n-i-p type PSCs. The photoelectrochemical, optoelectronic and thermal properties of the designed polymer and the photovoltaic performance of the devices are discussed. Forskning om perovskitsolceller (PSC:er) har genomgått en dramatisk utveckling sedan de första cellerna rapporterades 2009, och det senaste decenniet har sett ett betydande genombrott i deras effektomvandlingseffektivitet (PCE) från 3,8% till 25%. Den storskaliga industrialiseringen av PSC:er är emellertid fortfarande långt ifrån en enkel uppgift på grund av brist på högpresterande och billiga organiska håltransportmaterial (HTM). Därför är utvecklingen av nya generationer HTM önskvärt. Studierna i denna avhandling syftar till att utveckla nya, bill