Crosslinkable Amino‐Functionalized Conjugated Polymer as Cathode Interlayer for Efficient Inverted Polymer Solar Cells

Abstract

the optoelectronic properties, there are several requirements for interfacial materials, such as the formation of Ohmic contact between electrode and photoactive layer, [ 13 ] the appropriated surface energy of fi lm that can induce favorable phase segregation of bulk-heterojunction (BHJ) fi lms, [ 14,15 ] as well as the long-term chemical and physical stability. [ 8,16 ] Given that the fabrication of multilayer devices based on solution-processing techniques may suffer from interfacial erosion issue, the interlayers are required to be robust enough to tolerate the deposition solvents. [ 17 ] An effective approach to achieve robust interfacial layer is the utilization of crosslinkable materials, which has advanced solvent-resisting property and can prevent the potential erosion during sequential spin-coating procedure. [18][19][20] In this respect, a range of crosslinkable conjugated polymers have been developed as promising candidates for interfacial modifi cation. Conventional approaches to prepare crosslinkable conjugated polymers are chemically tethering functional groups such as oxetane groups, [ 21 ] alkyl-bromide, [ 22 ] azide, [ 23 ] and vinyl, [ 24 ] into the polymer chains. Based on these copolymers, crosslinked fi lms can be achieved through the crosslinking reactions triggered by either thermal or ultraviolet light. [ 25 ] However, the crosslinking reactions of functional groups typically require initiators, which may potentially decrease the device life-time. Although in some cases the initiators are not necessary, they need relative long time to attain a well crosslinked fi lm, which is unfavorable for the applications toward high-throughput R2R techniques. Thus, it is of vital importance to develop highly effi cient crosslinking strategy that can be accomplished under low activation energy, which bearing a fast reaction rate of the functional groups to reduce possible decomposition of the conjugated polymers during the crosslinking process.Click chemistry has been extensively investigated due to its advantages of highly selective, mild reaction conditions, easy purifi cation, and can give a wide range of molecular systems with high yields. [ 26,27 ] It is well-established that the "click" reaction of thiols and enes groups is very effi cient and can be fi nished within tens of seconds, [ 28,29 ] and most importantly, the reaction can be easily triggered by directly exciting thiol-groups upon the absorption of a photon of UV-light. [29][30][31]

Solution‐Processable Conjugated Polymers as Anode Interfacial Layer Materials for Organic Solar Cells

“…Compared with PEDOT:PSS, the OSC device using TPDSi 2 :TFB as AIL appeared to increase device performance due to electron block, better thermal stability, and stronger adhesion effects. [114] The robust crosslinked polymers covered on PEDOT:PSS films can induce the vertical composition distribution of donor:acceptor in the BHJ active layer, which facilitates the charge transport and charge collection by the electrodes. Therefore, there was a 2-fold increase in the PCE for the TPDSi 2 device.…”

Conjugated‐Polymer Blends for Organic Photovoltaics: Rational Control of Vertical Stratification for High Performance

“…Although the understanding of the mechanisms for vertical stratification is still under way, extensive research has proved that the vertical inhomogeneity of electron donors and acceptors in the cross‐section of the photoactive layer has a profound influence on device performance . This section will discuss how charge transport and collection can be affected in systems having different vertical stratifications, with the aim of guiding the design of a proper device architecture for high performance.…”

Insights into the working mechanism of cathode interlayers in polymer solar cells via [(C8H17)4N]4[SiW12O40]

“…S9 †). 45,46 So the charge carrier extraction time (s) of the PSCs are 1.73 ms for Al-only, 0.96 ms for LiF, 0.97 ms for PDINO and 0.94 ms for TASiW-12 derived from Fig. S9a.…”