There are a total of 56 11-letter words containing 'photo', and the number may vary in different dictionaries. You can specify the dictionary and order.

• multiphoton ₂₂
• photoactive ₂₃
• photobombed ₂₆
• photobomber ₂₅
• photocopied ₂₃
• photocopier ₂₂
• photocopies ₂₂
• photodiodes ₁₈
• photoessays ₁₈
• photofinish ₂₂
• photofloods ₂₁
• photographs ₂₃
• photography ₂₅
• photoionize ₂₆
• photolysing ₂₂
• photolyzing ₃₁
• photomapped ₂₆
• photometers ₁₉
• photometric ₂₂
• photomosaic ₂₂
• photomurals ₂₁
• photoperiod ₂₀
• photophases ₂₁
• photophobia ₂₄
• photophobic ₂₇
• photophores ₂₁
• photoreduce ₂₁
• photoresist ₁₆
• photosetter ₁₆
• photoshoots ₁₈
• photosphere ₂₁
• photostated ₁₇
• photostatic ₁₉
• photosystem ₂₁
• phototactic ₂₂
• phototrophs ₂₁
• phototropic ₂₂
• radiophotos ₁₇
• photoagings ₁₈
• phototaxies ₂₃
• photobathic ₂₃
• photochromy ₂₆
• photogenies ₁₇
• photoglyphs ₂₅
• photoglyphy ₂₈
• photoionise ₁₆
• photolithos ₁₉
• photonastic ₁₈
• photonovels ₁₉
• photophilic ₂₃
• photophobes ₂₃
• photophones ₂₁
• photophonic ₂₃
• phototropes ₁₈
• phototypies ₂₁
• phototyping ₂₂

There are 56 11-letter words containing photo in the well-known word game dictionary, 32 in the Scrabble US (US/Canada/Thailand - TWL/NWL) dictionary, and 51 in the Scrabble UK (International - SOWPODS/CSW) dictionary, and 38 in the Words with Friends (WWF) dictionary.