8470
Through controlled fabrication , high - to low - density nanohybrid networks are achieved , with low - density hybrid carbon nanotube networks tested as hole transport layers ( HTLs ) for bulk heterojunction ( BHJ ) organic photovoltaics ( OPV ) .
 Chemical: carbon
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: carbon 
Answer:
 Chemical: carbon