1. Report Speaker: C.A. Chen Teacher: G.S Liou 2013.11.15 Class: Special Topics on Polymers Synthesis

2. 2 Introduction of Polymer Solar Cells T ransparent electrode (ITO) Hole transport layer (PEDOT:PSS) Photoactive layer Ca/Al Conventional PSCs structure Advantages of PSCs: – Easy processing, low cost, low weight – Mechanical flexibility and transparency Current efficiency of PSCs: – Single junction: 10% (Mitsubishi Chemical) – Multi junction (tandem): 10.6% (UCLA) Bulk hetero junction photoactive layer (2) Solar spectrum (AM1.5) versus P3HT absorption spectrum (1) Ref 1: Boer, Polymer Reviews, 2008 Ref 2: Nano Today, 2010, 5, 231

3. Principle of Polymer Solar Cell ① Exciton generation ② Exciton diffusion* ③ Charge separation ④ Charge transport P-type: polymer N-type: PCBM anode cathode ① ② ③ ③ ④ ④ Energy P-type N-type FF=(V max *J max )/ (V oc *J sc ) V oc J sc V max J max *The distance of exciton diffusion: 5-14nm J sc is influenced by: 1. Absorption coefficient of materials 2. Morphology of blends of materials 3. Charge mobility of materials V oc is influenced by: Gap of energy levels of materials 3 A. B.Holmes et al, Appl. Phys. Lett., 1996, 68 (22), 3120-3122

4. Rational Design of Ideal Polymer A.J. Heeger et al., Adv. Mater., 2006, 18, 789–794. Donor Donor- Acceptor Acceptor Energy HOMO LUMO Donor Acceptor Low Bandgap Polymer n 4

5. Synthesize Low Bandgap Polymer Stille-coupling Suzuki-coupling Stille-coupling reaction and Suzuki-coupling reaction are useful for synthesizing alternating low bandgap polymers.

6. Conclusion Ideal polymers need: –Low cost –Easy synthesis –Low bandgap –Suitable HOMO and LUMO –High absorption coefficient –Broad UV-Vis absorption –High hole mobility –High Solubility Polymer solar cells can reach PCE~15% and be highly stable products in the future. T ransparent electrode (ITO) Hole transport layer (PEDOT:PSS) Photoactive layer Ca/Al