Acceptor Energy Level Control of Charge Photogeneration in Organic Donor/Acceptor Blends

Abstract

In this paper we focus upon the role of interfacial energetics in influencing the separation of charge transfer states into dissociated charge carriers in organic donor/acceptor blend films. In particular, we undertake transient optical studies of films comprising regioregular poly(3-hexylthiophene) (P3HT) blended with a series of perylene-3,4:9,10-tetracarboxydiimide (PDI) electron acceptors. For this film series, we observe a close correlation between the PDI electron affinity and the efficiency of charge separation. This correlation is discussed in the context of studies of charge photogeneration for other organic donor/acceptor blend films, including other polymers, blend compositions, and the widely used electron acceptor 3'-phenyl-3'H-cyclopropa[1,9](C(60)-I(h))[5,6]fullerene-3'-butanoic acid methyl ester (PCBM).

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

“…The inherited "excess energy" from the higher energy of excited states associating with the charge dissociation at the D/A interface has been well known as the hot exciton dissociation process in the OPV system [54,55]. The ultrafast hot exciton dissociation significantly contributes to photocurrent when absorbing low wavelength photons.…”

“…The CTs are more delocalized in nature and, thus, more prone to ultrafast charge separation instead of relaxation to the bound CT 1 state, which constitutes a loss path, due to a stronger coupling to the ground state. The excess energy of hot CT n states has been considered to be lost during relaxation to the "cold" CT 0 state, facilitates long-range charge separation [54,55].…”

Charge-Transfer State Dynamics Following Hole and Electron Transfer in Organic Photovoltaic Devices

“…11,35 To investigate the effect of the driving energy in more detail we performed ultrafast measurements on BTT-DPP:PC 70 BM devices for which the difference in the driving energy for electron-and hole-transfer scenarios is dramatically different. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure 4 presents the results of PPP experiment on a BTT-DPP:PC 70 BM cell.…”

Naphthodithiophene-Based Semiconducting Materials for Applications in Organic Solar Cells

“…The incorporation of angular-shape naphthodithiophene units results in more ordered microstructure and therefore higher hole mobility [63,66]. In M17-based solar cells, the big free energy di erence between the singlet photoexcited state of the donor material and the charge-separated state leads to e cient exciton separation and greatly prevents parasitic germinate electron-hole recombination [86]. The high hole mobility and large free energy di erence are in accordance with the enhanced Jscs and FFs.…”