29205
Using cross - sectional scanning tunneling microscope ( XSTM ) with samples cleaved in situ in an ultrahigh vacuum ( UHV ) chamber , this study demonstrates the direct visualization of high - resolution interfacial band mapping images across the film thickness in an optimized bulk heterojunction polymer solar cell consisting of nanoscale phase segregated blends of poly ( 3 - hexylthiophene ) ( P3HT ) and [ 6 , 6 ] - phenyl C61 butyric acid methyl ester ( PCBM ) .
 Chemical: poly ( 3 - hexylthiophene ); Chemical: P3HT; Chemical: [ 6 , 6 ] - phenyl C61 butyric acid methyl ester; Chemical: PCBM
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: poly ( 3 - hexylthiophene ); Chemical: P3HT; Chemical: [ 6 , 6 ] - phenyl C61 butyric acid methyl ester; Chemical: PCBM